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    <script>
        //特别注意：在非严格模式下函数的arguments和形参是一一映射的关系,改变arguments内部的值就是改变相关形参的值,当然在严格模式下,
        //改变arguments的值不会影响到形参的值
        // "use strict";
        var a = 4;

        function b(x, y, a) {
            console.log(a); //3
            arguments[2] = 10; //相当于a = 10
            console.log(a); // 10
        }
        a = b(1, 2, 3); //函数没有ruturn或者return没有写值他的返回值都是undefined
        console.log(a); //undefined
    </script>
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